Shaper which has a direct relationship between in and out.
Use in SIGMOID mode and use setTransitionPoint() in order to create double linear shaper.
May be referred to as Tween.LINEAR for use in setEasing().
LinearShaper()
LinearShaper( shapeMode )
LinearShaper( shapeMode, transition )
LinearShaper( shapeMode, transitionX, transitionY )
f(x){ x; }